Field of Endeavor
The present invention relates to chemical separation and more particularly to a system of separating chemical components of mixed fluid or multiple components dissolved in a solvent or carrier gas using a functionally graded material.
State of Technology
The present invention relates to separating a multicomponent mixture of chemicals into multiple streams enriched in an individual component or components. Processes exist for separating components of a fluid such as filtration, distillation, chromatography, and other separation techniques. For example; U.S. Pat. No. 5,160,625 describes “Field flow fractionation, a method obtaining high resolution separations of organic and inorganic colloids and soluble molecules, has been known in the art for approximately twenty years.” The patent states: “In field flow fractionation, a solution, having solute molecules dissolved therein, is made to flow through a working chamber formed in a fractionating conduit. Fluid flow in the working chamber is generally laminar in nature. The solute species is added in a concentrated form to a carrier solvent that is already present in and flowing through the working chamber. Usually, the construction of the working chamber is capillary in nature, i.e., having relatively small and generally uniform transverse cross-sectional dimensions in comparison to its axial length. The working chamber may have a simple cylindrical shape or may be of a generally rectangular cross-sectional configuration. In the case of a rectangular cross-sectional configuration, the working chamber has a depth substantially smaller than its width, so that solution flow through the working chamber is in the form of a thin layer. Under conditions of laminar fluid flow in a fractionating conduit, the flow velocity of any given fluid particle through the working chamber is a function of the distance of the fluid particle from the conduit wall. The velocity of a given fluid particle ranges from a maximum at a position midway between opposing conduit walls to a theoretical minimum of zero at the conduit wall. Thus, in the case of a rectangular working chamber, laminar fluid flow exhibits a velocity profile in the shape of a parabolic curve, the greatest velocity being at the transverse midpoint of the chamber. This velocity profile of the laminar fluid flow is advantageously used with the desired “field” to selectively separate or fractionate solute molecules from the flowing carrier solvent in the working chamber.’
Another example is U.S. Pat. No. 5,133,844 that describes “Field flow fractionation (FFF), pioneered by Giddings (Sep. Sci. 1966, 1, 123) is a versatile family of separation methods related to liquid chromatography. Since none of the subtechniques are utilizing a stationary phase for separation and therefore do not depend on an equilibrium process like classical chromatography, FFF is not in a strict sense a member of the family of chromatographic techniques. FFF involves the application of an external force field to a solution, causing a migration of its constituents towards the separation channel wall. Depending on the magnitude of the force field and on chemical/physical properties, a certain solute will eventually reach a certain concentration distribution resulting in a fixed distance from the separation channel wall, this process is called relaxation. If the solution in the channel is caused to move forward in a laminar way, a parabolic flow profile will develop and the constituents will move forward with velocities equal to that axial velocity vector where most of the solute is located.
The applied field may e.g. be thermal gradients (thermal FFF), centrifugal forces (sedimentation FFF), electrical forces (electrical FFF), transverse or lateral flow (flow FFF) and transverse pressure gradients (pressure FFF).”
Another example is United States Published Patent Application No. 2008/0179243 that states: “Historically, gradient based liquid phase chromatography has played a seminal role in molecular separation science. Originally limited to aqueous ion exchange chromatography, in recent years it has blossomed into numerous useful variations based on hydrophobic interactions and combinations of hydrophobic and hydrophilic interactions including a wide range of mobile and stationary phase chemistries. Despite this wide range of compositions, a universal feature of the current gradient technologies is a focusing of each band of eluted molecules because of increased binding to the stationary phase downstream and decreased binding upstream. This results in a velocity gradient in the eluted species that acts to counter the dispersive forces that would otherwise broaden the elution bands as they travel through the stationary phase. Concentrating eluted material into narrower bands is highly desirable because it leads to better separation of forms that elute at nearly the same conditions, a property known as selectivity, as well as providing a more homogeneous purified product. However, aside from the dispersive forces themselves, there is an intrinsic limitation to the focusing strength of these systems as relates to the challenge of selectivity. Generally, to achieve greater selectivity the gradient in eluent composition should be reduced. This increases the number of stationary phase volumes (or time) between an elution band and its nearest neighbors. Nevertheless, it also decreases the focusing strength of differential binding, so the peaks become broader as a function of stationary phase volumes. Since optimum selectivity is characterized by a maximum ratio of band separation to band width, called resolution, the tradeoff of flattening the gradients always leads to an optimal minimum slope.”